For several decades, loop type automobile sensing devices have been most widely used all over the world. Such a loop type automobile sensing device includes a loop coil installed in a cut portion of a road, and a loop sensor connected to the loop coil through a lead wire to detect the presence of an automobile through inductance variation, so as to detect traffic information on the presence, speeds and types of automobiles. This is because inductance variation of a loop coil is not affected by road icing, temperature/humidity variation, sunshine variation, and road surface conditions, and has a reliability of 99% or more in actual use. A loop type automobile sensing device detects inductance variation that is generated at a loop coil by the movement of an automobile to detect information on the presence, speeds and types of automobiles.
FIG. 1 is a schematic view illustrating an install state of a related art loop type automobile sensing device. Referring to FIG. 1, the loop type automobile sensing device includes a loop coil 1 that is embedded in a cut portion of a lane or region to be sensed, a loop sensing device 5, a lead line 3 connecting the loop coil 1 to the loop sensing device 5, and a controller 6 for using automobile sensing information.
FIG. 2 is a schematic view illustrating install states of related art loop coils. The loop coils include an 8-corner loop coil 25, a 32-angle loop coil 26, and a circular loop coil 27 that have a size of 1.8 m×1.8 m, a size of 4.0 m×1.8 m, and a diameter of 1.8 m, respectively.
FIGS. 3a through 3f are images illustrating a process of installing a related art loop coil in a road.
First, an outline is formed at an install region of a loop coil in a road as illustrated in FIG. 3a. Then, an automobile sensor head/lead-in is cut as illustrated in FIG. 3b. Then, foreign substances and water are removed from a cut portion and the cut portion is dried as illustrated in FIG. 3c. Then, the loop coil is installed in the cut portion as illustrated in FIG. 3d. Then, sealant is injected into the cut portion as illustrated in FIG. 3e. Finally, sealant flowing out of the cut portion is removed and the surrounding is cleaned to complete the process as illustrated in FIG. 3f. 
FIG. 4 is a schematic view illustrating an install state of a related art loop type automobile sensing device for sensing an automobile, and an install state of a camera applied to a nonpayment prevention system of a parking lot or a toll gate, a signal/speed enforcement camera, and a license plate recognition camera.
Referring to FIG. 4, the loop type automobile sensing device includes a loop coil 1 for sensing an automobile, a camera 19 for photographing an automobile, a loop sensing device (not shown) receiving a signal sensed at the loop coil 1 through a lead line 3, and the controller 6. The controller 6 detects speed violation or signal violation using a signal sensed at the loop sensing device, commands the camera 19 to form an image of a violation automobile, and processes the image.
The most characterized performance of the loop type automobile sensing device is its automobile sensing sensitivity. Much research shows that the automobile sensing sensitivity largely depends on the size of a loop coil and that the length of the minimum side of the closed loop coil is proportional to a sensing height. As a result, a standard loop coil has a small side of about 1.8 m in Korea (8-corner type: 1.8 m×1.8 m, 32-corner type: 4 m×1.8 m, circular type: diameter of 1.8 m).
Based on a relationship between loop coil size and automobile sensing sensitivity, a related art loop type automobile sensing device should have a predetermined size to maintain a desired automobile sensing sensitivity, which makes an install process complicated, thereby increasing install process time and costs.
In addition, since a road should be cut when installing a loop coil, the road is damaged. Further, after a road is repaved, an embedded loop coil is not recycled, thereby requiring additional costs. A frequent construction of a side of a road causes short circuiting of a connection wire between a loop coil and an automobile sensing device.
Referring to FIG. 5, after a loop type automobile sensing device 10 is installed on a side of a road, gas, electricity, and communication line constructions and road maintenance are frequently performed along an edge 11 of the road to cause short circuiting of a connection wire between the loop coil 1 installed in a lane and the loop type automobile sensing device 10 disposed at the side of the road. Thus, the life cycle of the loop type automobile sensing device 10 is very short. These limitations are common to related art methods of connecting the lead line 3 of the loop coil 1 to the loop type automobile sensing device 10 installed at the side of the road. As such, because of short circuiting of the lead line 3 between the loop coil 1 and the loop type automobile sensing device 10, equipment installed at an enormous cost becomes useless, thus significantly increasing social costs.
When modifying and maintaining a road including the loop coil 1, the thickness of the road is increased to decrease the automobile sensing sensitivity. In addition, the loop coil 1 is frequently broken down by careless modification and maintenance, thereby significantly increasing social costs.